fix(ci): auto-label new issues by area and assign owners

[yuanchen8911]

Summary

Automatically infer and apply area/* labels for newly opened issues, assign the configured area owners, and keep manual triage for ambiguous component selections. Also harden assignee normalization when reading .settings.yaml.

Motivation / Context

On main, the triage workflow adds needs-triage when an issue is opened, but area labels and assignees are only applied after a maintainer later adds an area/* label. That leaves straightforward, template-driven issues sitting in manual triage longer than necessary.

This change automates the common case by inferring the area from issue metadata and applying the configured owner immediately, while still preserving manual triage for cross-cutting or unknown issues.

Fixes: N/A
Related: N/A

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• Build/CI/tooling

Component(s) Affected

• Other: .github/workflows/triage.yaml

Implementation Notes

Inference chain (stops at the first match):

1. Existing area/* label already on the issue
2. Component dropdown from the issue template
3. Existing documentation label
4. Conventional commit scope in the title (for example, fix(bundler): ...)
5. Title keyword matching
6. Body keyword matching

Ambiguous component handling: Template dropdown values such as Multiple components, New component, and Other / Unknown intentionally stop inference and keep needs-triage for manual review.

Assignee normalization: Assignee values loaded from .settings.yaml are trimmed, unquoted, split on commas, filtered for empty entries, and deduplicated before calling addAssignees.

Testing

Verified by opening issues from the current templates and checking the resulting labels/assignees:

• Templated single-area issues received the expected area/* label and configured assignee(s)
• Ambiguous component selections stayed in needs-triage
• Existing documentation labels mapped to area/docs
• Duplicate or comma-separated assignee values are normalized before assignment

Also verified workflow syntax via CI (Lint Workflows) and full PR checks.

Risk Assessment

• Low — CI-only workflow change affecting issue triage automation

Rollout notes: N/A

Checklist

• Tests pass locally (make test with -race)
• Linter passes (make lint)
• I did not skip/disable tests to make CI green
• I added/updated tests for new functionality
• I updated docs if user-facing behavior changed
• Changes follow existing patterns in the codebase
• Commits are cryptographically signed (git commit -S)

[github-actions]

Coverage Report ✅

Metric	Value
Coverage	74.5%
Threshold	70%
Status	Pass

Coverage Badge

![Coverage](https://img.shields.io/badge/coverage-74.5%25-green)

No Go source files changed in this PR.